Modern aircraft are designed to carry, release, and deliver on target a wide variety of weapons including bombs, missiles, rockets and other stores which are hung on the underside of the aircraft and must be quickly released in flight. Various types of suspension and release equipment are used to carry the stores and safely separate the stores from the aircraft.
Currently available suspension and release equipment interfaces with lugs (generally referred to as bail lugs) which have screw threaded shanks received in tapped cavities formed in the stores, and integrally formed suspension rings for receiving hooks extending from the aircraft or bomb rack for carrying the store. Since these rings are aligned longitudinally relative to the store and aircraft, the lugs restrain the store longitudinally but provide little lateral support, thus the store tends to oscillate laterally under the influence of lateral accelerations or other aerodynamic effects. The store therefore requires supports such as sway braces to prevent lateral movement of the lug and store. Typically, the sway braces add aerodynamic drag to the aircraft and increase the radar cross-section of the aircraft. After release of the store from the aircraft, the bail lugs impose a significant drag penalty on the store during its flight. Other types of lugs eliminate the need for sway braces but still project outward from the store surface and have a large frontal area which adds aerodynamic drag to the store and increases the radar cross-section of the store.
These lugs were designed when aerodynamic drag of the lug on the store and the impact of the lug on the radar cross-section of the store were not important factors. Today the drag effect of the lug on the store and the impact to radar cross-section are more important with the higher launching speeds of present day high-performance aircraft and sophisticated bomb and radar systems. Various retractable lug devices are available, however these devices are complex, expensive to manufacture and add significant weight to the stores.
Moreover, the screw threaded shank design of the bail lug adds weight to the store by requiring a cavity for receiving the shank, with sufficient material formed around the cavity to retain the threaded shank. The threaded shank also adds weight to the lug along with machining costs. Furthermore, the cavity may compromise the functionality of certain stores and reduce their effectiveness.